1. Field of the Invention
The present invention relates to image formation apparatus and method which read images of originals fed from an original feeder and form the read images onto sheets.
2. Related Background Art
Conventionally, an image formation apparatus which performs double-faced copying from the first page of a double-faced original in due order has been known. FIGS. 9A, 9B, 9C and 9D respectively show the order of feeding of the double-faced originals, the order of image reading thereof, the order of image formation and the order of copy discharging in the case where the double-faced copying is conventionally performed from the double-faced originals. In the drawings, the case where two double-faced copies (i.e., duplicates) are obtained from the three double-faced originals is shown.
In this image formation apparatus (conventional example 1), an uppermost original sheet (also referred as simply "original" hereinafter) D1 being the first page of an original D put on an original tray is fed and carried to a read position on a platen. Then, after image reading on the front face (first page) of the original is performed, the original is reversed by a reverse path. The reversed original is again carried to the read position on the platen, and image reading on the back face (second page) of the original is performed.
Thus, the reading of the images of the double-faced original D1 ends. Next, the original is again reversed by the reverse path to adjust the order of the pages of the original on a sheet discharge tray of an original feeder, whereby the first page is discharged facedown to the sheet discharge tray. At the same time, feeding of a next original D2 to the platen starts, and as in the case of the original D1, the reading of the images of the third and fourth pages of the original is performed. Subsequently, the images of a double-faced original D3 are similarly read, and the original D3 is discharged to the sheet discharge tray. Thus, the images of the first to sixth pages of the originals D1 to D3 are sequentially read.
In case of forming double-faced images (i.e., images on the front and back faces of a recording sheet), the image of the first page of the original is first formed onto the first face of a sheet P1, and the operation waits for the image of the third page of the original to be read. Then, the image of the third page is read, and at the same time the image of the third page is formed onto the first face of a sheet P2. Similarly, the image of the fifth page is formed onto the first page of a sheet P3. The images of the first, third and fifth pages of the originals are formed at intervals necessary because of delay in reading the originals. Similarly, the image of the fifth page is formed onto the first page of a sheet P3. The images of the first, third and fifth pages of the originals are formed at intervals necessary because of delay in reading the originals.
If the image formation of the fifth page ends, the reversed sheet P1 is fed from a not-shown double-faced path to a transfer unit, the image of the second page is formed onto the second face of the sheet P1, and the sheet is discharged outside the apparatus with the image of the first page facedown.
Hereafter, the images are formed alternately onto sheets (P4, P5, P6) fed from cassettes and the sheet returned from the double-faced path, and the sheets to which the formation of the double-faced images ended are discharged outside the apparatus in due order.
FIGS. 10A, 10B, 10C and 10D respectively show the order of feeding of the double-faced originals, the order of image reading thereof, the order of image formation and the order of copy discharging in the other case where the double-faced copying is conventionally performed from the double-faced originals. In the drawings, like FIGS. 9A to 9D, the case where the two double-faced copies (i.e., duplicates) are obtained from the three double-faced originals is shown.
In this image formation apparatus (conventional example 2), an uppermost original sheet (also referred as simply "original" hereinafter) D1 being the first page of an original D put on the original tray is fed and carried to the read position on the platen (this operation is called as "blank carrying"). In this example, the image on the front face (first page) of the original is not read, the original is reversed by the reverse path, and the reversed original is returned to the read position on the platen. Next, the image on the second page (back face) of the original D1 is read. Then the original is again reversed by the reverse path, and the image on the first page (front face) of the original D1 is read.
Since the first page of the original faces downward in this state, if the original is discharged as it is, it is possible to adjust the order of the pages of the original on the sheet discharge tray of the original feeder. At the same time, feeding of a next original D2 to the platen starts, and as well as the case of the original D1, the images of the fourth and following pages of the original are read.
Hereinafter, the images are sequentially read in the similar manner, and finally the images of the second, first, fourth, third, sixth and fifth pages are read in that order.
In case of forming the double-faced images, the image of the second page of the original is formed onto the first face of a sheet P1, and the operation waits for the image of the fourth page of the original to be read. Then, the image of the fourth page is read, and at the same time the image of the fourth page is formed onto the first face of a sheet P2. Similarly, the image of the sixth page is formed onto the first page of a sheet P3.
If the image formation of the sixth page ends, the reversed sheet P1 is fed from the not-shown double-faced path to the transfer unit, and the image of the first page is formed onto the second face of the sheet P1. In this state, the second page of the original faces downward. If the original is discharged as it is, it is impossible to adjust the order of the pages of the original on the sheet discharge tray of the original feeder. Therefore, the sheet is reversed before it is discharged outward.
Hereafter, similarly, the images are formed alternately onto sheets (P4, P5, P6) fed from the cassettes and the sheet returned from the double-faced path, and the sheets to which the formation of the double-faced images ended are discharged outside the apparatus in due order.
However, in such the conventional image formation apparatus as described above, the following problems have occurred, so that improvement has been demanded.
Namely, in the conventional image formation apparatus (conventional example 1), in order to adjust the order of the pages of the original on the sheet discharge tray of the original feeder, it is necessary to reverse the sheet also when it is discharged. For this reason, it is necessary to perform the reverse operation twice while the image of one original is read.
Further, in the conventional structure, the carrying path to feed the original from the original tray to the platen and the reverse carrying path to reverse the original fed from the platen and return it to the platen are partially made in common to downsize the apparatus itself. Thus, it is impossible to feed the next original until the reverse operation for discharging the previous original ends.
As described above, productivity in a double-faced processing mode is low due to the factors on the original feeder side. Especially, when the numerous sheets are set to the original tray, decrease in productivity appears remarkably.
On the other hand, in the conventional image formation apparatus (conventional example 2), it is necessary to perform the reverse operation twice, i.e., one reverse operation before the image is read and one reverse operation after the image is read. Although this is similar to the conventional example 1, it is possible in the conventional example 2 to feed the next original simultaneously with the discharge of the previous original. Thus, it is possible in the conventional example 2 to make the original reading and discharging faster than the conventional example 1.
However, it is necessary to perform the reverse operation to adjust the order of the pages of the sheets to be discharged when the sheets to which the formation of the double-faced images ended are discharged outside the apparatus. Therefore, it is necessary to feed the sheets with appropriate intervals in consideration of the time required for such reverse operation, whereby productivity in the double-faced processing mode is low due to the factors on the image formation apparatus side.